linux-kernel - [PATCH 9/7] ipc/sem.c: Remove another memory barrier.

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Date:   Thu,  1 Sep 2016 17:27:53 +0200
From:   Manfred Spraul <manfred@...orfullife.com>
To:     benh@...nel.crashing.org, paulmck@...ux.vnet.ibm.com,
        Ingo Molnar <mingo@...e.hu>, Boqun Feng <boqun.feng@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, will.deacon@....com,
        1vier1@....de, Davidlohr Bueso <dave@...olabs.net>,
        Manfred Spraul <manfred@...orfullife.com>
Subject: [PATCH 9/7] ipc/sem.c: Remove another memory barrier.

As spin_unlock_wait() is defined as equivalent to spin_lock();
spin_unlock(), the memory barrier before spin_unlock_wait()
is not required.

Signed-off-by: Manfred Spraul <manfred@...orfullife.com>
---
 ipc/sem.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index a5da82c..2bef9c0 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -280,11 +280,7 @@ static void complexmode_enter(struct sem_array *sma)
 		return;
 	}
 
-	/* We need a full barrier after seting complex_mode:
-	 * The write to complex_mode must be visible
-	 * before we read the first sem->lock spinlock state.
-	 */
-	smp_store_mb(sma->complex_mode, true);
+	sma->complex_mode = true;
 
 	for (i = 0; i < sma->sem_nsems; i++) {
 		sem = sma->sem_base + i;
-- 
2.7.4